Equipment Change Delay

After the end of casting a skill, there is always a delay in changing the equipment of all the characters. Certain items are assigned in my keys (I'm using BM [Battle Mode]). For example, after casting a skill, I change my Moonlight hat to my Hokage hat but it doesn't change immediately. There's this note on the Regular Log that says "You can't put this item on." There are a few seconds delay before I can change my equipment. What gives?